Every time I run Fluent, it iterates between 50,000 to 70,000 iterations and then it freezes. And when I restart it, it starts from the first iteration, and repeats the cycle again. So does anyone knows how to save my iterations, so that when it freezes I can just load the last saved iterations and continue from where it stopped?

Under the Solution menu there should be Calculation Activities where you can set up an auto-save every X number of iterations (for example 1000 or 100, I usually go for however many iterations fits inside a 15-30 minute window). This could potentially mean a large number of saved files and disk space used, but that's why we have the Edit button in the Autosave window where you can tick the box "Retain only the most recent files" and select to retain maybe 1 or 2 of them (so Fluent will delete the last saved data file each time two new ones are saved).